CN114210311B

CN114210311B - Germanium adsorbent, preparation method and method for recycling germanium

Info

Publication number: CN114210311B
Application number: CN202111531537.7A
Authority: CN
Inventors: 赵飞平; 袁睿; 张传龙; 向鸿锐; 胡文吉豪; 柴立元; 闵小波; 林璋; 唐崇俭
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-05-05
Anticipated expiration: 2041-12-14
Also published as: CN114210311A

Abstract

The invention provides a preparation method of a germanium adsorbent, which comprises the following steps: s1, swelling chitosan in acetic acid solution to obtain transparent pasty swelling chitosan; s2, mixing EDC, NHS and tartaric acid, and then carrying out a pre-reaction at the temperature of-8 ℃ to 2 ℃ to obtain a pre-treatment liquid; s3, carrying out a modification reaction on the pretreatment liquid and the swelling chitosan, and adjusting the pH value of the reaction liquid to 8.5+/-0.05 after the modification reaction is finished so as to separate out the germanium adsorbent from the reaction liquid. The preparation method is environment-friendly, simple and convenient to operate and has higher adsorptivity to germanium. Based on the preparation method, the invention also provides a germanium adsorbent and a method for recycling germanium, which are used for efficiently adsorbing and recycling germanium in waste liquid.

Description

Germanium adsorbent, preparation method and method for recycling germanium

Technical Field

The invention relates to the field of germanium recovery, in particular to a germanium adsorbent, a preparation method and a method for recovering germanium.

Background

Germanium (Ge) is a typical rare-earth element with a relatively high melting point and a relatively brittle texture, and is an important semiconductor metal with an abundance of only 15 parts per million in the crust. Germanium has stable chemical property, can react with strong acid such as aqua regia only under heating, and has valence electron configuration of 4s ² p ² The configuration accords with the copper ion valence electron configuration. The oxides and sulfides of germanium on earth exist mainly in the form of GeS ₂ GeO and GeO ₂ Etc. In addition, germanium has various special properties, and has wide and important application in the fields of semiconductors, aerospace measurement and control, nuclear physical detection, optical fiber communication, infrared optics, solar cells, chemical catalysts, biomedicine and the like, thereby being an important strategic resource. Germanium has wide application in medicine field, and can be used for preventing and treating cancer, and organic compounds in germanium compounds can be used as toothpaste, high-efficiency analgesic paste, etc. Thus, germanium is now becoming a strategic resource for urgent demands of various countries.

However, germanium is very little in the ore, and the process of extracting germanium element from the ore is highly demanding and difficult. With the development of technology, the consumption and demand of germanium are increasing, but germanium resources are lacking and supply is not needed, so that the efficient recycling of germanium is becoming important. Conventional germanium recovery technologies, such as precipitation and extraction, may cause serious environmental pollution, and the loss rate of extracted germanium is high, so that many limitations exist for practical application.

In order to solve the above problems, for germanium recovery, chitosan is widely paid attention to as a biomass-based adsorption material, which is abundant in source, green and degradable and has a structurally abundant amino group. There have been studies on adsorption of germanium using chitosan to separate and recover germanium. However, although the existing adsorption method using chitosan has the disadvantages of simple operation, low treatment cost and wide application range, the original structure of chitosan is not particularly ideal for the recovery performance of germanium, and the adsorption efficiency of chitosan still needs to be improved.

In view of the foregoing, there is a need for a germanium adsorbent, a method of making, and a method of recovering germanium that addresses or at least alleviates the above-described drawbacks of low adsorption efficiency of germanium.

Disclosure of Invention

The invention mainly aims to provide a germanium adsorbent, a preparation method and a method for recycling germanium, and aims to solve the technical problem of low adsorption efficiency of germanium.

In order to achieve the above object, the present invention provides a method for preparing a germanium adsorbent, comprising the steps of:

s1, swelling chitosan in acetic acid solution to obtain transparent pasty swelling chitosan;

s2, mixing EDC, NHS and tartaric acid, and then carrying out a pre-reaction at the temperature of-8 ℃ to 2 ℃ to obtain a pre-treatment liquid;

s3, carrying out a modification reaction on the pretreatment liquid and the swelling chitosan, and adjusting the pH value of the reaction liquid to 8.5+/-0.05 after the modification reaction is finished so as to separate out the germanium adsorbent from the reaction liquid.

Further, in the step S1, the volume concentration of the acetic acid solution is 2 to 10%;

in the step S2, the mixing process is performed in a mixed solution of water and ethanol.

Further, in the step S1, the swelling reaction time is 1.5-2 hours, and the swelling reaction temperature is 25-30 ℃.

Further, in the step S2, the pre-reaction is performed under the condition of ice bath, and the duration of the pre-reaction is 1-1.5 h;

in the step S3, the modification reaction is carried out at a temperature of 25-30 ℃, and the modification reaction time is 11-13 h.

Further, the swollen chitosan: the tartaric acid: the EDC: the molar ratio of NHS is 1:1 to 3:3:1.

further, in the step S3, the pH of the reaction solution is adjusted to 8.5 after the completion of the modification reaction.

The invention also provides a germanium adsorbent, which is prepared by adopting the preparation method of the germanium adsorbent.

The invention also provides a method for recycling germanium, which comprises the following steps: mixing the germanium adsorbent according to claim 7 with a germanium-containing solution to be treated, controlling the pH of the germanium-containing solution or the mixed solution to be 0.5-7, and vibrating the mixed solution to finish the adsorption of germanium by the germanium adsorbent.

Further, the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated is 0.5-2mg:1mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500mg/L.

Further, the mixed solution is kept at 25-30 ℃ and is subjected to vibration adsorption for 5min-24h at the vibration speed of 140-160 rpm.

Compared with the prior art, the invention has the following advantages:

1. the invention swells chitosan by adopting acetic acid, adopts EDC and NHS to mediate tartaric acid to react with chitosan to generate germanium adsorbent, has larger adsorption capacity to germanium in solution under the specific pH value condition, and the whole adsorption process can reach equilibrium within about 200 min; in addition, the germanium adsorbent can be stably dispersed in a solution after being subjected to specific modification, and can be regenerated and recycled; compared with the original unmodified chitosan, the chitosan grafted and modified by tartaric acid has the advantages of greatly improved adsorption capacity, short adsorption equilibrium time and full utilization of adsorption sites.

2. The method is environment-friendly and simple and convenient to operate, and the reagents used in the method are nontoxic and harmful, so that no waste liquid is discharged in the whole material synthesis and adsorption process, and no pollution is caused to the environment; in addition, the method carries out modification and modification on chitosan by using tartaric acid, EDC and NHS through a simple liquid phase synthesis method, has simple and convenient synthesis process operation, and can realize mass synthesis.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic illustration of the reaction scheme of a grafting process in a method for preparing a germanium adsorbent according to the present invention;

FIG. 2 is a schematic illustration of the chemical reaction of germanium adsorbent and germanium combination in accordance with the present invention;

FIG. 3 is a scanning electron microscope image of TA-CS and CS in example 1; wherein a is 4000 times of CS, b is 4000 times of TA-CS, and c is 1000 times of TA-CS;

FIG. 4 is an EDS diagram of the element distribution of TA-CS in example 1;

FIG. 5 is a graph showing the respective element ratios of TA-CS and CS in example 1;

FIG. 6 is a chart of Fourier infrared transformation spectra of TA-CS and CS in example 1;

FIG. 7 is an X-ray photoelectron spectrum of TA-CS and CS in example 1;

FIG. 8 is a graph showing adsorption performance of TA-CS and CS on germanium at different acidity in example 2;

FIG. 9 is a graph of adsorption performance of TA-CS and CS at different germanium concentrations and an isotherm fit thereof in example 2;

FIG. 10 is a graph showing adsorption performance of TA-CS and CS at different adsorption times in example 2.

The achievement of the object, functional features and advantages of the present invention will be further described with reference to the drawings in connection with the embodiments.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

It should be noted that all directional indicators (such as upper and lower … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.

Moreover, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the embodiments, and when the technical solutions are contradictory or cannot be implemented, it should be considered that the combination of the technical solutions does not exist, and is not within the scope of protection claimed by the present invention.

In order to obtain a material with high adsorptivity to germanium, the invention provides a preparation method of a germanium adsorbent, which comprises the following steps:

s1, swelling chitosan in acetic acid solution to obtain transparent pasty swelling chitosan. Wherein, in the swelling reaction process, stirring can be continuously carried out so as to ensure that the swelling chitosan is in a transparent pasty state. The volume concentration of the acetic acid solution is 2-10%, and may be specifically 5%.

In addition, in order to allow the swelling reaction to proceed sufficiently, the time of the swelling reaction may be 1.5 to 2 hours, and the reaction temperature of the swelling reaction may be 25 to 30 ℃.

S2, mixing EDC (1- (3-dimethylaminopropyl) -3-ethylcarbodiimide), NHS (N-hydroxysuccinimide) and tartaric acid, and then carrying out pre-reaction at the temperature of-8-2 ℃ to obtain a pre-treatment liquid. Wherein, the pre-reaction is mainly used for leading tartaric acid to be introduced on a chitosan structure in a grafting way, thereby improving the modification efficiency of chitosan.

In addition, the mixing of EDC, NHS and tartaric acid may be performed in a mixed solution of water and ethanol. In order to ensure that the temperature at the time of the reaction is around zero, the pre-reaction is carried out under ice bath conditions. In order to fully perform the pre-reaction, the duration of the pre-reaction is 1 to 1.5 hours, and the duration of the reaction can be specifically 1 hour.

S3, carrying out a modification reaction on the pretreatment liquid and the swelling chitosan, and adjusting the pH value of the reaction liquid to 8.5+/-0.05 after the modification reaction is finished, wherein the pH value can be specifically adjusted to 8.5 so as to separate out the germanium adsorbent from the reaction liquid, thereby obtaining the separated germanium adsorbent.

The chemical structural formula of the germanium adsorbent is as follows:

in order to ensure that the modification reaction is sufficiently carried out, the modification reaction can be carried out at a temperature of 25-30 ℃, the duration of the modification reaction can be 11-13 h, and the duration of the reaction can be 12h.

As a preferable ratio of the present embodiment, the swelling chitosan: the tartaric acid: the EDC: the molar ratio of NHS may be 1:1 to 3:3:1. since the swollen chitosan obtained in the step S1 is a transparent pasty liquid and contains acetic acid, it should be noted that the amount of the substance corresponding to the swollen chitosan in the above ratio is not calculated in the process of calculating the ratio, and the substances such as acetic acid doped in the swollen chitosan are not calculated.

In the above embodiment, the hydrogen bond in the chitosan molecule can be broken by the aqueous solution of acetic acid, so that the chitosan is fully swollen into a uniform liquid state having a certain viscosity. The obtained swelling chitosan is not precipitated and dried by alkali, but directly utilizes liquid swelling chitosan, and quantitatively reacts with tartaric acid in a grafting way by a volumetric equal ratio method to obtain the germanium adsorbent, so that the germanium adsorbent has uniform components and reliable quantification, and acetic acid molecules can be used as a subsequent acetylation promoting reagent. Wherein the volumetric equivalent method, i.e. the volumetric replacement mass, can replace the previously calculated mass of solid chitosan with the volume, since the liquid swollen chitosan is homogeneous and its original solid mass is proportional to the now liquid volume.

In the preparation process of the embodiment, tartaric acid molecules are grafted on chitosan through a chemical mediated method, specific steps of chemical mediation are defined, each step is refined and specific to the reaction process, the stability and sufficiency of the reaction can be ensured, the temperature of the reaction is ensured to be about zero in the pre-reaction stage, and the stable intermediate is used for promoting the acetylation reaction.

It should also be clear that the germanium adsorbent uses good complexing property of tartaric acid on germanium, grafts the tartaric acid as a monomer molecule on low-cost biomass-based material chitosan, and can realize good adsorbent capacity as a modified adsorbent, and on the basis, the germanium adsorbent can be recycled through desorption, thereby reducing cost and being environment-friendly.

As an explanation of the grafting process described above, reference is made to fig. 1: the complex acid (tartaric acid) containing carboxylate and EDC are coupled to produce lipid material, and because EDC is generally applicable in pH=3-5, the lipid material produces protonizing phenomenon under acidic condition, and the product is reacted with NHS to make electron transfer and deprotonation to produce NHS ester material, and the intermediate is stabilized by ice bath, and the carboxylate is activated and has high reactivity, and can produce amide bond when it is fully reacted with chitosan containing amino group, so that tartaric acid can be successfully grafted onto chitosan and can remove NHS. EDC and NHS in the grafting process are combined for the main purpose of improving the coupling efficiency of the reaction, and an ice bath in the process is mainly used for stabilizing the generated ester intermediate so as to further promote the amide reaction.

Based on the preparation method of the germanium adsorbent, the invention also provides the germanium adsorbent, which is characterized in that the preparation method of the germanium adsorbent in any embodiment is adopted to prepare the material with high adsorption effect on germanium.

As an application of the germanium adsorbent, referring to the germanium adsorption process shown in fig. 2, the present invention also provides a method for recovering germanium, comprising: mixing the germanium adsorbent according to any of the above embodiments with a germanium-containing solution to be treated, controlling the pH of the germanium-containing solution or the mixed solution to be 0.5-7, and then vibrating the mixed solution to complete the adsorption of germanium by the germanium adsorbent.

Wherein, in order to improve the adsorption efficiency of the germanium adsorbent to germanium, the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated may be 0.5-2mg:1mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500mg/L.

In addition, in the adsorption process, the mixed solution can be kept at 25-30 ℃ to be subjected to vibration adsorption for 5min-24h at the vibration speed of 140-160 rpm.

For a further understanding of the invention, an illustration is now given:

example 1

Preparation and characterization of tartaric acid modified chitosan adsorbent

Process for the preparation of (I)

1) Weighing 10g of Chitosan (CS), preparing 5% acetic acid solution, putting 10g of chitosan into 500mL of 5% acetic acid solution to swell for two hours, stirring by a magnetic stirrer, and breaking intermolecular hydrogen bonds by acetic acid to form transparent pasty swelling chitosan liquid (CS-L);

2) 10mL of water, 10mL of ethanol, 3.568g of EDC, 0.714g of NHS and 2.793g of tartaric acid are stirred and mixed by a magnetic stirrer, and are reacted for 1h by adopting an ice-ice bath mode to obtain a pretreatment liquid;

3) Taking 50mL of prepared swelling chitosan, adding the prepared pretreatment solution into 50mL of swelling chitosan, stirring and mixing by a magnetic stirrer, and keeping the reaction at 30 ℃ for 12 hours; after the reaction was completed, the pH was adjusted to 8.5 to precipitate a tartaric acid-modified chitosan adsorbent (TA-CS).

(II) characterization

1. SEM analysis

As shown in FIG. 3, it can be seen that the TA-CS has a coarser surface and a porous structure, so that the TA-CS has a larger specific surface area, which is beneficial to adsorption treatment.

The element distribution of TA-CS is shown with reference to FIG. 4, which is converted from a color map; specifically, as shown in fig. 5, it can be seen from the figure that the proportion of C, N, O element in CS is 94.09%, 0.46% and 5.45%, the proportion of C, N, O element in TA-CS is 86.13%, 0.78% and 13.09%, respectively, and the proportion of oxygen element after tartaric acid modification is significantly increased.

2. ATR analysis

As shown in FIG. 6, 3400cm of ATR spectra of CS and TA-CS ^-1 Nearby telescopic vibration absorption peak corresponding to N-H bond and O-H bond in CS and TA-CS, 1070cm ^-1 The vicinity corresponds to the characteristic absorption peak of C-O. Compared with CS, the main characteristic peak variation of TA-CS and CS is embodied in 1000-2000 cm ^-1 The range is 1620cm ^-1 And 1380cm ^-1 The nearby stretching vibration peak is due to an amide bond in the tartaric acid grafted chitosan, which indicates that the tartaric acid and the chitosan are successfully compounded.

3. XPS analysis

As shown in fig. 7, fig. 7 is an X-ray photoelectron spectroscopy total graph of the tartaric acid-modified chitosan adsorbent and the unmodified chitosan adsorbent in example 1. In the C1s graph of TA-CS, from the fitting result, bonds formed between carbon elements and other elements in TA-CS include three types, namely 287.69eV is C=O, 285.99eV is C-O, and 284.51eV is C-C; the bonds formed between the nitrogen element and other elements in TA-CS include two types, namely 401.16eV is-NH ⁺ ₃ 398.97eV is-NH ₂ 。

Compared with the original CS, TA-CS-NH ₂ Peak area ratio-NH of unmodified chitosan ₂ The peak area is small while the c=o bonds increase relative to the peak area, and the analysis is probably due to the increased density of c=o bonds by amide bonds, which laterally verifies that tartaric acid was successfully incorporated into the chitosan structure in a grafted fashion.

The peak areas of the peaks are specifically shown in the following table:

example 2

Adsorption performance of TA-CS and CS on germanium

Under optimized experimental conditions, preparing germanium ion solution with concentration of 1000mg/L, and gradient diluting to different concentrations (0.5-500 mg/L), using HNO ₃ And NaOH solution to adjust the pH to the desired value (0.5-7). The pH tester is a pH meter (pHS-3G, shanghai Lei Ci); the germanium ion concentration was measured by ICP-OES measuring instrument, 3 samples were takenAnd selecting the minimum value of the RSDs as a data reference with the adsorption band value.

1. Adsorption performance of TA-CS and CS on germanium at different pH values

The initial germanium concentration is fixed at 30mg/L, 7mg of TA-CS and 7mg of CS are respectively mixed with 7mL of aqueous solution containing germanium ions, the fixed adsorption temperature is 30 ℃, and the mixture is oscillated for 24 hours in an oscillation box at 150 r/min.

As shown in the correspondence between pH and adsorption capacity in FIG. 8, it can be seen that TA-CS has lower adsorption performance on germanium, less than 5mg/g, under peracid or neutral conditions. And at a pH of 0.5-3, its adsorption capacity increases with increasing pH and reaches a maximum of 28.19mg/g at pH 3. For CS, the adsorption effect on germanium ions under the super-acidic condition is good, and reaches the maximum value at the pH of 2, and analysis is probably due to the fact that the amino protonation effect on the chitosan structure under the acidic condition promotes the adsorption of the germanium ions, and the saturated adsorption amount of CS on germanium is 6.38mg/g at the pH of 3.

2. Adsorption performance of TA-CS and CS on germanium at different germanium concentrations

The pH of the initial germanium solution was fixed at 3, 7mg of TA-CS and 7mg of CS were mixed with 7mL of germanium-ion-containing aqueous solution, the fixed adsorption temperature was 30℃and the mixture was shaken in a shaking box at 150r/min for 24 hours.

As shown in FIG. 9, data of adsorption of germanium (0.5-500 mg/L) at different concentrations by TA-CS and CS are shown, and FIG. 9 shows that CS langmuir fitting corresponds to CS in the figure and TA-CS langmuir fitting corresponds to TA-CS in the figure.

When the concentration of the germanium solution is 0-200mg/L, the adsorption capacity of the TA-CS is increased along with the increase of the concentration of the germanium solution, and reaches a saturated state at 200mg/L, the concentration is continuously increased to 500mg/L, and the adsorption capacity of the TA-CS is not increased any more. By fitting the adsorption isotherms of TA-CS and CS, the fitting data are shown in the following table, and the result shows that the TA-CS reaches the maximum adsorption capacity of 53.42mg/g, which is about 13 times that of the original unmodified chitosan (4.04 mg/g), and the adsorption performance of the chitosan on germanium is greatly improved by tartaric acid modification, and the material has good application performance on the recovery of germanium.

3. Adsorption performance of TA-CS and CS on germanium under different adsorption time

The initial germanium concentration is fixed at 30mg/L, the pH of the initial germanium solution is 3, 7mg of TA-CS and 7mg of CS are respectively mixed with 7mL of germanium ion-containing aqueous solution, the fixed adsorption temperature is 30 ℃, and the mixture is subjected to oscillation adsorption in an oscillation box of 150 r/min.

As shown in FIG. 10, adsorption experiments of TA-CS and CS on germanium were performed at different reaction times (0.5, 1, 2, 5, 10, 30, 60, 240, 480, 960 and 1440 min). The adsorption of TA-CS to germanium is rapidly increased in the first 240min, the adsorption quantity is basically unchanged from 240min to 1440min, and the dynamic balance of the adsorption reaction is achieved. The maximum adsorption capacity of TA-CS to germanium is 25mg/g, and a plurality of adsorption sites on the surface of TA-CS are rapidly occupied by germanium ions in the initial stage of adsorption, and are represented by solvent diffusion, then the adsorption of germanium is continued through various actions such as complexation, ion exchange and the like, and finally the adsorption equilibrium site is reached in 240 min.

In the above technical solution of the present invention, the above is only a preferred embodiment of the present invention, and therefore, the patent scope of the present invention is not limited thereto, and all the equivalent structural changes made by the description of the present invention and the content of the accompanying drawings or the direct/indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method of recovering germanium comprising: mixing a germanium adsorbent with a germanium-containing solution to be treated, controlling the pH of the germanium-containing solution or the mixed solution to be 0.5-7, and vibrating the mixed solution to finish the adsorption of the germanium by the germanium adsorbent;

the preparation method of the germanium adsorbent comprises the following steps:

s3, carrying out a modification reaction on the pretreatment liquid and the swelling chitosan, and adjusting the pH value of the reaction liquid to 8.5+/-0.05 after the modification reaction is finished so as to separate out the germanium adsorbent from the reaction liquid;

wherein the swollen chitosan: the tartaric acid: the EDC: the molar ratio of NHS is 1:1 to 3:3:1.

2. the method for recovering germanium according to claim 1, wherein in the step S1, the volume concentration of the acetic acid solution is 2 to 10%;

3. The method for recovering germanium according to claim 1, wherein in the step S1, the time of the swelling reaction is 1.5 to 2 hours, and the reaction temperature of the swelling reaction is 25 to 30 ℃.

4. The method for recovering germanium according to claim 1, wherein in the step S2, the pre-reaction is performed under ice bath conditions, and the duration of the pre-reaction is 1 to 1.5 hours;

5. The method for recovering germanium according to any one of claims 1-4, wherein in step S3, the pH of the reaction solution is adjusted to 8.5 after the completion of the modification reaction.

6. The method of recovering germanium according to claim 1, wherein the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated is 0.5-2mg:1mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500mg/L.

7. The method for recovering germanium according to claim 1 or 6, wherein the mixed solution is kept at 25 to 30 ℃ and subjected to vibration adsorption at a vibration rate of 140 to 160rpm for 5min to 24h.